In the practice of peritoneal dialysis, a dialysate is admitted to the peritoneal cavity of the patient through either a permanently implanted peritoneal catheter or more commonly through the use of a stab catheter. Such catheters have a perforated peritoneum section which lies within the peritoneal cavity. The catheter then extends exterior to the patient's body permitting the introduction of the dialysate from an external source.
The need for efficient peritoneal dialysis may be required either as a chronic medical treatment or in response to an acute medical episode. Renal failure is a common cause giving rise to the need for medical intervention through the use of peritoneal dialysis.
Peritoneal dialysis is often the preferred route of dialysis offering significant advantages over hemodialysis. While it is accepted that hemodialysis is more efficient than peritoneal dialysis, in the critically ill patient, peritoneal dialysis is often preferred because it allows for smoother fluid toxin and solute removal than hemodialysis. This may be necessary because of the patient's cardiovascular instability. Hemodialysis is not universally available. Many smaller hospitals do not have the necessary equipment to perform hemodialysis and therefore peritoneal dialysis would be the treatment of choice. Hemodialysis is very costly since expensive machines must be purchased and a nurse is required to be present for the duration of the procedure. This is not so for peritoneal dialysis, especially with the use of permanent catheter implantation. The increased convenience and decreased costs associated with peritoneal dialysis are significant advantages. Hemodialysis also requires a vascular access route into the patient which may not be available in some instances.
Efficient peritoneal dialysis is critical to patient care. Hypertonic dialysis fluid is instilled in the peritoneal cavity. Toxins in the bloodstream will diffuse through the peritoneal membrane along a concentration gradient into the peritoneal cavity, and water flows in similar direction along an osmotic gradient. As these toxins and other waste byproducts accumulate in the peritoneum, the concentration differentials decrease and the rate at which the toxins are removed from the bloodstream is reduced. Also, as glucose enters the blood stream from the dialysis fluid, the osmotic gradient for fluid removal diminishes with time. Continuous replacement of dialysis fluid in the peritoneal cavity will maintain these gradients providing optimal fluid and solute removal. Therefore to achieve efficient dialysis, the maintenance of a substantial concentration differential and the osmotic gradient between the blood vessels and the peritoneal cavity is essential.
At the present time, there are other catheters available which function as permanently implanted peritoneal dialysis devices. However, these devices are limited as to the maximum efficiency which can be achieved by the fact that they are single lumen devices. Reference would be drawn to U.S. Pat. No. 4,392,855.
There are dual lumen catheters in the marketplace which serve other purposes. For example, a number of patented devices can be found for hemodialysis and continuous blood sampling: U.S. Pat. Nos. 4,493,696; 4,583,968; 4,405,313; 4,626,240 and 4,601,697. Other dual lumen devices exist in the marketplace including devices of more general application (U.S. Pat. No. 701,075), devices for drainage of surgical fields (U.S. Pat. No. 3,528,427) and devices for intestinal intubation (U.S. Pat. No. 2,614,563).
The cited dual lumen hemodialysis patents can be differentiated from the present invention on the basis that they have been devised to address the unique problems arising in venous catherization, for example, ensuring ease of entry into the vein so as to prevent any kinking or buckling. To overcome this difficulty, venous catheters have been inventively adapted with smooth bore, semi-flexible, semi-rigid tips. This modification (seen in U.S. Pat. Nos. 4,493,696; 4,626,240; 4,583,968) permits the catheter to gently bend so as to yield to the shape of the vein yet retain sufficient rigidity so that the risk of kinking or buckling is minimized. A similar result is achieved in U.S. Pat. No. 4,405,313 by "filling-in" the area around the two tubes at the distal end of the catheter.
At present, all known peritoneal dialysis catheters, but one, have only a single lumen (U.S. Pat. No. 4,392,855; Tenckhoff and Schechter "A Bacteriologically Safe Peritoneal Access Device", Trans. Amer. Soc. Artif. Int. Organs, Vol XIV, 1968, pp 181-187). The Buyer's abdominal drainage tube, (U.S. Pat. No. 2,930,378) does exhibit a dual lumen structure, but it is distinguishable from the present invention in that both the inner tube and outer tube are perforated. The Buyer's device is suitable merely for drainage and could not function as a dual lumen dialysis device. The mixing of fluids between the inner and outer tubes would make it impossible to achieve the continuous flow dialysis envisioned by the present inventor. Furthermore, the overall structure of the Buyer's abdominal drainage tube would impede, if not render impossible, the necessary subcutaneous tunnelling required for permanent implantation.
The one remaining peritoneal dialysis catheter, which does have a double lumen structure similar to that of the applicant, is that of Nakamura, T. et al, "Continuous Peritoneal Dialysis with a Double Lumen Catheter for Acute Renal Failure in a New Born after Cardiac Surgery", Japanese Journal of Intensive Care Medicine, Vol 7, page 837, 1983The Japanese peritoneal catheter is a straight, rigid device designed as a "stab" catheter.